Working in QGIS 3 x64 with built-in python console and editor.

I have a list of the feature IDs of duplicate features in my dataset. Ultimately, I want each of these features to have a value of 1 for the field error.

When I run the following block of code, the correct number of duplicate features prints, so that's not a problem. It's when I go to update error to 1.

Code so far:

geoms = dict()
dup_features = list()
null_features = set()

features = layer.getFeatures()
index = QgsSpatialIndex()

for current, f in enumerate(features):
    if not f.hasGeometry():

    geoms[f.id()] = f.geometry()

unique_features = dict(geoms)

for feature_id, geometry in geoms.items():
    if feature_id not in unique_features:

    candidates = index.intersects(geometry.boundingBox())

    for candidate_id in candidates:
        if geometry.isGeosEqual(geoms[candidate_id]):


## problem section of code

for feature in dup_features:
    feature['error'] = 1 ## Line 58 referred in error

Error generated:

    File "<string>", line 58, in <module>
TypeError: 'int' object does not support item assignment

Alternatives Tried: (none of these throw errors but don't update the attribute value)

for feature_id in dup_features:
    feature['error'] = 1
for feature_id in dup_features:
    feature['error'] = 1
  • The code looks ok to me - can you clarify what issue you experience with the code?
    – ndawson
    Jan 15, 2019 at 20:17
  • Updated question, let me know if you still need more clarification
    – jyingling
    Jan 16, 2019 at 14:29

1 Answer 1


Once you have some duplicate feature ids stored in your list e.g.

dup_features = [9, 10, 11]

Try replacing those troublesome lines with something like this:

fld_id = layer.fields().lookupField('error')

for feature_id in dup_features:
    fid = feature_id
    atts = {fld_id: 1}
    layer.dataProvider().changeAttributeValues({fid: atts})

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